WO1998039297A1

WO1998039297A1 - Compositions for safening rice against acetochlor

Info

Publication number: WO1998039297A1
Application number: PCT/GB1998/000578
Authority: WO
Inventors: Don Robert Baker; Richard Lynn Franz; Khosro Khodayari; Jeff Kimo Curtis
Original assignee: Zeneca Limited
Priority date: 1997-03-04
Filing date: 1998-02-24
Publication date: 1998-09-11
Also published as: ID23866A; AU735943B2; KR20000075774A; CN1249746A; EP0970051A1; AU6302798A; JP2001513808A; BR9807645A

Abstract

This invention relates to safeners, herbicide compositions and methods of their use and more particularly, to safened acetochlor compositions and their use on rice. The safeners are of formula (I) wherein: R is hydrogen, C1-C6 alkyl, C1-C6 haloalkyl or C1-C6 alkoxy-C1-C6 alkyl; R1 is hydrogen, halogen, C¿1?-C6 alkyl, C1-C6 haloalkyl or C1-C6 alkoxy-C1-C6 alkyl; and X is hydrogen, halogen, C1-C6 alkyl, C1-C6 haloalkyl or C1-C6 alkoxy-C1-C6 alkyl; with the proviso that at least one of X and R1 is not hydrogen.

Description

COMPOSITIONS FOR SAFENING RICE AGAINST ACETOCHLOR

FIELD OF THE INVENTION

This invention relates to safeners, herbicide compositions and methods of their use and more particularly, to safened acetochlor compositions and their use on rice.

BACKGROUND OF THE INVENTION

The need for effective herbicides needs no special emphasis. The control of weeds and undesirable vegetation is of great economic importance since weed competition inhibits the production of foliage, fruit or seed and agricultural crops. The presence of weeds can reduce harvesting efficiency and the quality of the harvested crop. Thus, suppression of undesirable weed growth is very advantageous.

Herbicides are generally used to control or eradicate weed pests on a variety of crops. The particular emphasis of the instant invention is the suppression of undesirable weeds at the locus of rice plants. Herbicides are useful because they increase rice yields and reduce harvest costs.

Some herbicides may injure rice plants at application rates necessary to control weed growth. To be effective, an herbicide must cause at most minimal damage to the rice plant while maximizing injury to weed species which infest the locus of the rice plant. To preserve the beneficial aspects of herbicides which injure plants beyond an acceptable level, many herbicide safeners have been prepared. These safeners reduce or eliminate damage to the rice plant without substantially impairing the damaging effect of the herbicide on weed species. The herbicide used in this invention is 2-chloro-N-(ethoxymethyl)-6'-ethyl-o- acetotoluidide. It has the common name acetochlor and has the following chemical structural formula:

The safening of acetochlor for some crop species is known in the art. For instance, U.S. Patent No. 4,964,893 ("Brannigan et al."), incorporated herein by reference, discloses acetochlor safening in sorghum, corn and soybean. In addition, the same patent discloses a well known herbicide, butachlor, 2-chloro-2',6'-diethyl-N-(butoxymethyl) acetanilide, use on rice with an appropriate safener. However, the use of acetochlor on rice plants is not disclosed.

Brannigan et al. disclose a few phenyl (3-pyridinyl) compounds but both aromatic rings are unsubstituted. The compounds disclosed herein possess a substituent on the phenyl ring or on the pyridine ring. It is believed the substitution of the 4-position of the pyridine ring increases the safening activity of these compounds. Substitution of the phenyl group also increases activity.

The compounds disclosed herein have been found to be especially useful for safening rice against acetochlor. As discussed more fully below, rice may be grown or cultured using a variety of methods. The following is a description of different rice culturing methods:

In the postflood postemergence (transplanted) method, rice is grown to the 2-4 leaf stage away from the field. The field is flooded and tilled (puddled) until a blend of mud is achieved. The rice plants are then transplanted into this mud. Herbicide application typically takes place before or after flooding. In the postflood postemergence (water seeded) method, rice is soaked for 24 or more hours, then is sown to the surface of a shallow flooded field. Herbicide application is typically after weed germination.

In the preflood postemergence direct seeded (broadcast or drilled) method, rice is broadcasted or planted with a planter under the soil surface. The field may be flushed (watered) to promote rice growth. The field is flooded 1 week or more after this planting as the plants germinate. Herbicide application takes place typically before this flood, but after emergence of the rice plants.

In the preflood postemergence (South East Asia style) method, rice is soaked for 24 or more hours. The field is puddled to the right consistency and drained. The pre- germinated seeds are then broadcast to the surface of the soil. Flooding takes place as the rice develops. Herbicide application normally takes place before the flooding, but after the emergence of the rice plants.

Finally, in the preemergence or delayed preemergence method, seeds are planted usually with a planter of sorts. Herbicide application is made before emergence of the rice or weeds.

In China, acetochlor has been applied for weed control in rice in a postflood. postemergence application at very low concentration levels of active ingredient. However, this use has not produced good results because no safener is employed and thus the rice plants suffer phytotoxic effects.

In general, safening activity is determined empirically by observing the complex interaction of several factors. Some of these factors include the interaction of the herbicide compound, the type of weed to be controlled, the crop to be protected, and the safening compound itself.

Although the use of acetochlor on other crop species is known, it was thought to be too injurious to rice at the concentration levels necessary for effective weed suppression. Surprisingly, the inventors have found that acetochlor may be used on rice plants at effective levels when a safener is employed. High levels of weed control are possible with acetochlor and with the appropriate safener, rice injury is reduced to an acceptable level.

SUMMARY OF THE INVENTION

In one aspect, this invention is directed to compounds useful as safeners,

compounds of formula (I)

wherein:

R is hydrogen, Cι-C₆ alkyl, C C₆ haloalkyl or Cι-C₆ alkoxy-C_t-C₆ alkyl;

R¹ is hydrogen, halogen, Cι-C₆ alkyl, CpC₆ haloalkyl or Cι-C₆ alkoxy- - alkyl; and

X is hydrogen, halogen, Cι-C₆ alkyl, C[-C₆ haloalkyl or Cι-C₆ alkoxy-C_rC alkyl; with the proviso that at least one of X and R¹ is not hydrogen.

In another aspect, this invention is directed to an herbicidal composition comprising,

a) an herbicidally effective amount of acetochlor; and

b) a non-phytotoxic antidotally effective amount of a compound according to formula (I),

wherein:

R, R¹ and X are as defined above.

In yet another aspect, this invention is directed to a method for reducing injury to a rice plant, said injury due to acetochlor. comprising applying to an area of the plant and/or locus thereof a non-phytotoxic antidotally effective amount of a compound of formula (I),

wherein:

R, R¹ and X are as defined above.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, this invention is directed to compounds of the formula (I)

wherein:

R is hydrogen, Cι-C₆ alkyl, Cp , haloalkyl or C C₆ alkoxy-Cι-C₆ alkyl;

R¹ is hydrogen, halogen, C|-C₆ alkyl, Cι-C₆ haloalkyl or Cι-C₆ alkoxy-Cι-C₆ alkyl; and

X is hydrogen, halogen, C)-C₆ alkyl, Cι-C₆ haloalkyl or - alkoxy-Cι-C₆ alkyl; with the proviso that at least one of X and R¹ is not hydrogen.

The preferred compounds are methyl phenyl-(4-chloro-3-pyridyl)-methoxyacetate (compound 1. Table I); phenyl-(4-chloro-3-pyridyl)-methoxyacetic acid (compound 2, Table I); and ethyl o-tolyl-(3-pyridyl)-methoxyacetate (compound 3, Table I).

a) an herbicidally effective amount of acetochlor; and

wherein:

R, R¹ and X are as defined above.

The preferred compounds are methyl phenyl-(4-chloro-3-pyridyl)-methoxyacetate (compound 1, Table I); phenyl-(4-chloro-3-pyridyl)-methoxyacetic acid (compound 2, Table I); and ethyl o-tolyl-(3-pyridyl)-methoxyacetate (compound 3, Table I).

wherein:

R. R¹ and X. are as defined above.

The formulae given above are intended to include any physically distinguishable modifications of the compounds which may arise, for example, from different ways in which the molecules are arranged in a crystal lattice, or from the inability of parts of the molecule to rotate freely in relation to other parts, or from geometrical isomerism, or from intramolecular or lntermolecular hydrogen bonding, or otherwise. As employed herein, the word "halogen" includes fluoro, chloro, bromo and lodo groups

The terms "herbicide" and "herbicidal" are used herein to denote the inhibitive control or modification of undesired plant growth Inhibitive control and modification include all deviations from natural development, such as total killing, growth retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, leaf burn and dwarfing. The term "herbicidally effective amount" is used to denote any amount which achieves such control or modification when applied to the undesired plants themselves or to the area in which these plants are growing. The term "plants" is intended to include germinated seeds, emerging seedlings and established vegetation, including both roots and above- ground portions

The terms "antidote", "safening agent", "safener", "antagonistic agent", "interferant", "crop protectant" and "crop protective", are often-used terms denoting a compound capable of reducing the phytotoxicity of a herbicide to a crop plant or crop seed. The terms "crop protectant" and "crop protective" are sometimes used to denote an herbicide-safener combination which provides protection from competitive weed growth by reducing herbicidal injury to a valuable crop plant while at the same time controlling or suppressing weed growth occurring in the presence of the crop plant. An "antidotally effective amount" of an antidote or safener is that amount which protects crop plants by interfering with the herbicidal action of a herbicide on the crop plants, but without interfering with the herbicidal action on weeds, so as to render the herbicide selective to weed plants emerging or growing in the presence of crop plants.

The safener is applied in conjunction with acetochlor in a non-phytotoxic antidotally effective amount. By "non-phytotoxic" is meant an amount which causes at most minor or no injury to the desired rice plant. The preferred weight ratio of acetochlor to safener is from about 0.1.1 to about 30 1. An even more preferred weight ratio range is from about 2.1 to about 2.5 The synthesis of 4-substituted pyridyl-3-carbinols is disclosed in U.S. Patent No. 5,308,826 which is incorporated herein by reference. In general, the compounds of Formula I may be prepared by (A) reacting a substituted pyridine of the formula (III):

with a substituted benzaldehyde of the formula (IV):

wherein R and X are as defined for formula (I) above; in the presence of a suitable base to form a 3-pyridyl carbinol of formula V;

and (B) reacting such pyridyl carbinol with an alkyl-bromoacetate (example methyl bromoacetate BrCH CO₂CH₃), to produce a compound of formula I.

Typically, about 1-2 equivalents of an appropriate base (such as lithium diisopropylamide or n-butyl lithium) is added to a substituted pyridine of formula (HI) in a solvent (such as ethylene glycol dimethyl ether, tetrahydrofuran, diethyl ether or the like) at a temperature of between about -100° and about -40° C. After suitable blending, about 1-2 equivalents of the substituted benzaldehyde (IV) is generally added.

This reaction mixture is typically agitated and slowly warmed up to ambient temperature (about 25° C.) over a period of 1-24 hours. The reaction is then generally quenched by the addition of a saturated aqueous ammonium chloride solution or aqueous hydrochloric acid. The pyridyl carbinol so produced may be recovered by conventional techniques (such as extraction, filtration and the like) and purified by known methods, e.g., flash chromatography.

In the second step, the pyridyl carbinol (V), in a suitable solvent (such as tetrahydrofuran, methylene chloride, or the like) may typically be added to between about 1 and about 4 equivalents of an appropriate base (such as sodium hydride or triethylamine) at about 0° C. Between about 1 and about 3 equivalents of derivatizing agent is then added and the mixture agitated until complete. The reaction may be quenched by the addition of ice water, and the products recovered by conventional techniques, such as extraction, filtration and the like. The product so recovered may then be purified by conventional techniques such as flash chromatography or the like.

The substituted pyridine starting materials of Formula (III) are either commercially available or may be prepared by one or ordinary skill in the art employing methods such as those described in "Heterocyclic Compounds. Pyridine and its Derivatives", R.A. Abramovitch, Vol. 14, Wiley, 1973. The aldehyde starting materials of Formula (IV) are commercially available or may be prepared employing techniques such as those described in "Survey of Organic Synthesis", CA. Buehler et al., Vols. 1 and 2. Wiley-Interscience, 1970.

FORMULATIONS

A formulation is the incorporation of a formulant in a form which is directly usable on crops and weeds. As defined herein, a "formulant" is the material which is to be formulated. The formulant may be either an antidote compound alone or an herbicide and antidote composition. The purpose of the formulation is to apply the formulant to the locus of a crop where it is desired to establish herbicidal selectivity by a convenient method. The "locus" may include soil, seeds, crop, crop seeds, seedlings and vegetation.

The antidotes described herein can be formulated in a number of ways for suitable application: (a) the antidote can be formulated for application directly to the crop seed; (b) the antidote and herbicide may be formulated separately and applied separately or applied simultaneously in an appropriate weight ratio, e.g., as a tank mix, or (c) the antidote and herbicide may be formulated together in the proper weight ratio.

The choice of formulation and mode of application for any given composition may affect its activity, and selection will be made accordingly. The composition of the invention may thus be formulated as wettable powders, as emulsifiable concentrates, as powders or dusts, as flowables, as solutions, suspensions or emulsions, granules or in controlled-re lease forms such as microcapsules. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. The optimum amount for any given composition will depend upon the species of rice and its environment. The rate of application will generally vary from about 0.01 to about 11.5 kilograms per hectare, preferably from about 0.02 to about 4.5 kilograms per hectare.

Wettable powders are in the form of finely divided particles which disperse readily in water or other liquid carriers. The particles contain the active ingredient retained in a solid matrix. Typical solid matrices include fuller's earth, kaolin clays, silicas and other readily wettable organic or inorganic solids. Wettable powders normally contain about 5% to about 95% of the active ingredient plus a small amount of wetting, dispersing, or emulsifying agent.

Emulsifiable concentrates are homogeneous liquid compositions dispersible in water or other liquid, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthas, isophorone and other nonvolatile organic solvents. In use, these concentrates are dispersed in water or other liquid and normally applied as a spray to the area to be treated. The amount of active ingredient may range from about 0.5% to about 95% of the concentrate. Dusts are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids which act as dispersants and carriers.

Granules are in the form of small pellets of clay or other matrix designed to sink to the bottom of a flooded field then release the active ingredient.

Microcapsules are typically droplets or solutions of the active material enclosed in an inert porous shell which allows escape of the enclosed material to the surrounds at controlled rates. Encapsulated droplets are typically about 1 to 50 microns in diameter. The enclosed material typically constitutes about 50 to 95% of the weight of the capsule, and may include solvent in addition to the active compound. Shell of membrane materials include natural and synthetic rubbers, cellulosic materials, styrene-butadiene copolymers, polyacrylonitriles, polyacryiates, polyesters, polyamides, polyureas, polyurethanes and starch xanthates.

Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a solvent in which it is completely soluble at the desired concentration, such as water, acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurized sprayers, wherein the active ingredient is dispersed in finely-divided form as a result of vaporization of a low boiling dispersant solvent carrier may also be used.

Many of these formulations include wetting, dispersing or emulsifying agents. Examples are alkyl and alkylaryl sulfonates and sulfates and their salts; polyhydric alcohols; polyethoxylated alcohols; esters and fatty amines. These agents when used normally comprise from 0.1% to 15% by weight of the formulation.

Each of the above formulations can be prepared as a package containing the herbicide together with other ingredients of the formulation (diluents, emulsifiers, safeners, surfactants, etc.). In addition, the herbicide and safener may be individually formulated. The formulations can also be prepared by a tank mix method, in which the ingredients are obtained separately and combined at the grower site. 3 CT/GB98 --^"

EXAMPLES

The following examples are intended to further illustrate the present invention and are not intended to limit the scope of this invention in any manner whatsoever.

EXAMPLE I

Methyl phenyl-(4-chloro-3-pyridyl)-methoxyacetate (Compound 1) .

A. To a stirred -70°C solution of benzaldehyde (approx. 7.0 grams) in tetrahydrofuran was added approximately 1 equivalent of a 4-chloropyridyl lithium salt. The solution was allowed to warm to 25°C and after 45 minutes was quenched with a saturated ammonium chloride solution. Next, the solution was extracted with diethyl ether and a saturated sodium chloride solution. The organic phase was recovered and dried over magnesium sulfate. The solvent was stripped under reduced pressure to yield about 10 grams of the crude intermediate product of formula V, 4-chloro-3-(hydroxy- benzyl)pyridine. The crude product was titrated with 50% diethyl ether/pentane to yield 3.9 grams of pure 4-chloro-3-(hydroxy-benzyl)pyridine. The product was confirmed by gas chromatography/mass spectrometry analysis.

B. To a 0°C solution of 4-chloro-3-(hydroxy-benzyl)pyridine (2 grams, 9 mmol.) from part A above, potassium iodide. 18-Crown-6. and methyl bromoacetate (1.8 grams, 1.2 eq) in dimethyl formamide was added sodium hydride (60%, 0.44 grams, 1.2 eq) . The reaction mixture was allowed to warm to 25°C and was stirred for 2 days. The solution was subsequently quenched with a saturated ammonium chloride solution and extracted with diethyl ether. Next, the organic solution phase was washed with water and dried over magnesium sulfate. The crude product was purified by column chromatography using a diethyl ether/pentane solvent system. The yield was 1.6 grams of compound 4, which was a light oil. EXAMPLE 2 Phenyl-(4-chloro-3-pyridyl)-methoxyacetic acid (Compound 2).

To the product in Example 1, part B above, (0.5 grams) in 20 mL of ethanol was added a sodium hydroxide solution (about 7mL, 10% NaOH) and the solution was stirred at 25°C for 2 hours. Next, diethyl ether was added and extracted twice with a dilute sodium hydroxide solution. Subsequently, the solution was acidified to pH 6 and extracted three times with chloroform. The organic extracts were combined and dried over magnesium sulfate. The solution was stripped under reduced pressure. The yield was 0.19 grams of a soft solid.

EXAMPLE 3 Ethyl o-tolyl-(3-pyridyl)-methoxyacetate (Compound 3).

A. To 3-pyridylaldehyde (5.8 grams, (1.1 eq) in 100 mL of tetrahydrofuran at - 50°C was added 1.0 N o-toluylmagnesuium bromide( 50 mL, 1 eq). The solution was warmed to -10°C for 30 minutes. Next, the reaction mixture was quenched with a saturated solution of ammonium chloride and extracted with diethyl ether. The organic phase was washed with a saturated sodium chloride solution and dried over magnesium sulfate. The solution was evaporated under reduced pressure to yield 8.0 grams of a solid product. The product was confirmed by gas chromatography/ mass spectrometry.

B. To a solution of 3-(hydroxy-2'methylbenzyl) pyridine (8 grams, 40 mmol.), 18- crown-6, potassium iodide and ethyl bromoacetate (10 grams, 1.5 eq) in dimethyl formamide was added sodium hydride (60%, 2.0 grams, 1.2 eq). The reaction mixture exothermed to 65°C. The solution was allowed to stir and was return to 25°C over 2 hours. Next, 200 mL of water was added and extracted twice with ethyl acetate. The organic phase was dried over magnesium sulfate and evaporated under reduced pressure to yield 10 grams of crude product. The crude product was chromatographed using a ethyl acetate/pentane solvent system to yield l.lg. brown oil. The structure of product was confirmed by gas chromatography/mass spectrometry. TABLE I

Comp. No. R R¹ X

1 CH₃ H 4-CI

2 H H 4-Cl

The compounds in Table I are effective safeners of acetochlor on rice.

HERBICIDAL SCREENING TESTS

The compounds listed in the foregoing Table I were tested for herbicidal activity by the method below and at various rates of application. The results of some of these tests are given below. Results obtained in herbicidal screening are affected by a number of factors including: the amount of sunlight, soil type, soil pH, soil organic matter, temperature, humidity, depth of planting, plant growth stage, application method, application rate as well as many other factors. All testing procedures are administered with the least amount of variability possible. State of the art equipment and techniques are employed to enable the screening process to remain consistent and reliable.

PRE FLOOD POST EMERGENCE HERBICIDAL SCREENING TEST

Seeds of Echinochloa crus-galli ("ECHCG") were seeded V2 centimeter (cm) deep into 8.9 X 8.9 cm pots. The pots were previously filled with puddled clay soil which contained 2.2% organic matter and a pH of 5.7. In addition, the rice hybrid "Kaybonnet" (Orγsa Sativa) was also seeded in pots to a depth of 1 cm.

The pots were placed into 10 liter plastic tubs lined with plastic bags. The tubs were sprayed with the test material in acetone/water 50:50 with 0.5% Tween 20® (a surfactant) at a rate of 200 grams acetochlor/ha and 500 grams/ha safener at the growth stages of 2-3 leaf both rice and ECHCG. The tubs were flooded with water to a depth of 2- 3 cm 7 days after application

The degree of rice phytoxicity was evaluated and recorded 7 days after treatment (DAT) and compared to the growth of the rice plants of the same age in an untreated control flat. In addition, the degree of weed control/rice phytoxicity was evaluated and recorded 28 DAT as a percentage of control as compared to the growth of the same species of the same aεe in an untreated control flat.

Percent control is the total injury to the plants due to all factors including: inhibited emergence, stunting, malformation, albinism, chlorosis, necrosis and other types of plant injury. The control ratings range from 0 to 100 percent, where 0 represents no effect with growth equal to the untreated control and where 100 represents complete kill. Representative results are shown in Table II. TABLE II PRE-FLOOD POST EMERGENCE

COIUIP. NO. RICE 7 DAT RICE 28 DAT ECHCG 28 DAT

1 0 0 0

0 0 0 0

3 0 0 0 acetochlor 55 44 100

1+ acetochlor 5 17 100

2+ acetochlor 8 12 100

3+ acetochlor 8 3 100

Although the invention has been described with reference to preferred embodiments and examples thereof, the scope of the present invention is not limited only to those described embodiments. As will be apparent to persons skilled in the art, modifications and adaptations to the above-described invention can be made without departing from the spirit and scope of the invention, which is defined and circumscribed by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A compound of formula (I)

wherein:

R is hydrogen, C╬╣-C₆ alkyl. C_rC₆ haloalkyl or -C₆ alkoxy- -C_╧î alkyl;

R¹ is hydrogen, halogen, C╬╣-C₆ alkyl, C[-C₆ haloalkyl or C╬╣-C₆ alkoxy- - alkyl; and

X is hydrogen, halogen, C╬╣-C alkyl, C|-C₆ haloalkyl or C╬╣-C alkoxy-C_t-C₆ alkyl; with the proviso that at least one of X and R¹ is not hydrogen.

2. A compound according to claim 1. wherein R is hydrogen.

3. A compound according to claim 1 , wherein R is C╬╣-C₆ alkyl.

4. A compound according to claim 1, wherein R is - alkyl; R is hydrogen; and X is halogen.

5. A compound according to claim 1, wherein R is methyl; R¹ is hydrogen; and X is chloro.

6. A compound according to claim 1, wherein R is hydrogen; R . 1 i :.s hydrogen; and X is chloro.

7. A compound according to claim 1, wherein R is ethyl; R is methyl; and X is hydrogen.

8. An herbicidal composition comprising, a) an herbicidally effective amount of acetochlor; and

wherein:

R is hydrogen, CpC alkyl, C╬╣-C₆ haloalkyl or C|-C₆ alkoxy-C C alkyl;

R¹ is hydrogen, halogen. C|-C₆ alkyl, C╬╣-C₆ haloalkyl or C╬╣-C₆ alkoxy-C╬╣-C₆ alkyl; and

X is hydrogen, halogen, -C₆ alkyl, C,-C₆ haloalkyl or C C₆ alkoxy-C╬╣-C₆ alkyl; with the proviso that at least one of X and R¹ is not hydrogen.

9. An herbicidal composition according to claim 8, wherein R is hydrogen.

10. An herbicidal composition according to claim 8, wherein R is C╬╣-C₆ alkyl.

11. An herbicidal composition according to claim 8, wherein R is - alkyl;

R is hydrogen and X is halogen.

12. An herbicidal composition according to claim 8, wherein R is hydrogen;

R is hydrogen and X is halogen.

13. A method for reducing injury to a rice plant, said injury due to acetochlor, comprising applying to an area of the plant and/or locus thereof a non-phytotoxic antidotally effective amount of a compound of formula (I),

wherein:

R is hydrogen, C╬╣-C₆ alkyl, C╬╣-C₆ haloalkyl or CpC₆ alkoxy-C╬╣-C₆ alkyl;

R¹ is hydrogen, halogen, C╬╣-C₆ alkyl, C╬╣-C₆ haloalkyl or C╬╣-C₆ alkoxy-C╬╣-C₆ alkyl; and

X is hydrogen, halogen, -C₆ alkyl, C╬╣-C₆ haloalkyl or -C₆ alkoxy-C╬╣-C₆ alkyl; with the proviso that at least one of X and R¹ is not hydrogen.

14. A method for reducing injury to a rice plant according to claim 13 wherein R is hydrogen.

15. A method for reducing injury to a rice plant according to claim 13 wherein R is C,-C₆ alkyl.

16. A method for reducing injury to a rice plant according to claim 13 wherein R is d-C alkyl; R¹ is hydrogen and X is halogen.

17. A method for reducing injury to a rice plant according to claim 13 wherein R is hydrogen; R¹ is hydrogen and X is halogen.